Starter motor circuit with fast reset means

ABSTRACT

A control circuit for the starter motor of an engine has rapid acting and reliable means for automatically reattempting starting in the event that the pinion gear of the starter motor fails to engage the driven gear of the engine due to tooth abutment or other causes. A time delay relay periodically reopens the pinion gear shifting solenoid circuits until such time as the pinion gear is engaged at which point the time delay means is inactivated while the engine is being cranked. The quick precise response of the circuit is of particular value in connection with emergency motor-generator installations designed to start automatically in response to an electrical power failure and which do not have an operator in attendance to actuate a starter motor.

United States Patent [19] Wagner STARTER MOTOR CIRCUIT WITH FAST RESETMEANS [75] Inventor: Harold H. Wagner, Peoria, 111. [73] Assignee:Caterpillar Tractor Co., Peoria, 111. [22] Filed: Oct. 13, 1971 I 21Appl. No.: 188,969

[52] US. Cl. 123/179 BG, 123/179 86 [51] Int. Cl. F02n 17/00 [58] Fieldof Search 123/179 B, 179 BG [56] References Cited I UNITED STATESPATENTS 2,991,370 7/1961 Sutton 123/179 B 2,988,079 6/1961 Voigt..123/179 3,259,753 7/1966 'McWhirter t. 290/38 3,071,125 l/l963Leaver.... 123/179 3,443,557 5/1969 Herbert... 123/179 3,415,999 12/1968 Noury 290/38 [451 July 10, 1973 AttorneyDonald J. McRae and Fryer,Tjensvold.

Feix, Phillips & Lempio [57] ABSTRACT A control circuit for the startermotor of an engine has rapid acting and reliable means for automaticallyreattempting starting in the event that the pinion gear of the startermotor fails to engage the driven gear of the engine due to toothabutment or other causes. A time delay relay periodically reopens thepinion gear shifting solenoid circuits until such time as the piniongear is engaged at which point the time delay means is inactivated whilethe engine is being cranked. The quick precise response of the circuitis of particular value in connection with emergency motor-generatorinstallations designed to start automatically in response to anelectrical power failure and which do not have an operator in attendanceto actuate a starter motor. I

2 Claims, l-Drawing Figure CIRCUIT WITH FAST RESET.

MEANS BACKGROUND OF THE INVENTION STARTER MOTOR engine has started.Shifting of the pinion gear into en-' gagement is accomplished byelectrically energizing a pinion solenoid which is itself energizedthrough a starting relay. In the absence of corrective measures, anattempt toengage the pinion gear in this manner may fail because of acondition termed a butt engagement. This is a condition where the teethof the pinion gear and of the engine gear do not have the right relativeangular positions to engage. Instead, one end of the teeth of one gearabut the ends of the teeth of the other.

Various means have been employed to reduce the occurrence of buttengagements which, aside from failing to start the engine, can havevarious undesired effects such as accelerated gear wear and overheatingof solenoids or other circuit components. One such technique consists ofbeveling the adjacent ends of the teeth on the two gears and othersinvolve imparting a slight rotation to the pinion gear as it is advancedtowards the engine gear. None of these means are fully effective toprevent butt engagements. Tests of one commonly used starter motorsystem produced a butt engagement for approximately every thirtyattempted starts.

Although it is an annoyance, such an occurrence does not cause an overlysevere problem in instances where an operator is controlling the startersuch as in an automotive vehicle. Starter systems generally have meansfor indexing the pinion gear each time the system is actuated and if abutt engagement occurs it is evident to the operator who then releasesthe starter button or the like momentarily and reattempts starting ofthe engine. In certain systems, a butt engagement can be a more serioussituation in that an operator is not present to momentarily deactivatethe starter circuit, Starter motors are often employed, for example, instandby power systems designed to start up automatically in response tofailure of electrical utility power. In certain situations, such as inhospitals for example, starting up of the standby power system must beboth extremely reliable and extremely rapid. Accordingly such systemsrequire means for detecting a butt engagement and for momentarilydeenergizing the pinion solenoid to initiate repeated attempts at piniongear engagement until the engine is being cranked. The circultsheretofore used for this purpose have been undesirably slow andirregular with respect to response time. One commonly used system, forexample employs a thermostatic switch through which the pinion shiftingsolenoid current passes. The switch is heated by the heavy current untila bi-metalic element distorts to open the switch. This process usuallytakes several seconds and another several seconds are required for theswitch to cool and reclose to initiate a second attempt at engagement ofthe pinion gear. This is not only an undesirably long time but the timeinterval varies considerably in response to different externalconditions such as the initial temperature of the switch, degree ofenclosure of the switch and other variables. The switch remains in thecircuit and draws current while the starter motor is in the process ofcranking the engine.

SUMMARY OF THE INVENTION The present invention is a starter motorcontrol circuit which very rapidly and consistently resets to reattemptpinion gear engagement until such time as the starter motor is crankingthe engine. For this purpose a precision time delay relay having lowcurrent requirements momentarily interrupts the starting solenoidcircuit a predetermined time after each energization, to reset theentire circuit, until such' time as the pinion gear is engaged. At thatpoint the time delay'relay 'is in effect isolated from the circuit anddoes not receive current while the starter motor is cranking the engine.

Accordingly, it is an object of this invention to decrease the averagetime required to start an engine with an electrical starter motor inresponse to start signals. It is another object of this invention toprovide means for resetting a starter motor circuit at periodicintervals until engagement of the starter motor pinion gear with anengine gear is completed which means is consistent with respect totiming of the resetting operation and which is inactivated when thestarter motor is in the process of cranking the engine.

Theinvention, together with further objects and advantages thereof, willbest be understood by reference to the following description of apreferred embodiment taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWING- The accompanying drawing is apartially broken out view of a typical starter motor and pinionsolenoidtherefor together with a control circuit according to the inventionshown in diagramatic form.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing, thecontrol circuit 11 of the present invention is adaptable to a startermotor assembly 12 which may be of conventional construction and whichwill therefore beherein described only to the extent necessary tounderstand the coaction of the control circuit therewith. Such a startermotor assembly 12 may includean electrical motor l3 having DC powerterminals 14 and having an armature shaft 16 which rotates when power isapplied to the terminals. Shaft 16 extends into a housing 17 containingan axially movable pinion gear 18 disposed coaxially with respect to theshaft and coupled thereto through an overrunning clutch 19 which ismovable axially along the shaft with the pinion gear and through helicalsplines 20 which act to index the pinion gear during each axialmovement. An opening 21 is provided in housing 17 to receive a portionof an engine gear 22 of the-associated engine and which is cranked inorder to start the engine. The gears 18 and 22 are positioned so thatwhen pinion gear 18 together with overrunning clutch 19 are movedaxially along shaft 16 toward motor 13 the two gears are'disengagedwhile when the Pinion gear 18 and clutch are shifted away from motor 13the two gears are brought into engagement. To provide for this axialmotion of the pinion gear 18 and clutch 19, a shifting clutch collar 23is disposed on shaft 16 and is engaged by a shift lever 24 which ispivoted to housing 17 by a pin 26 whereby the lever may be pivoted tomove the collar in the direction of engine gear 22. A compression spring27 is disposed coaxially with respect to shaft 16 between collar 23 andclutch 19 whereby such motion of the clutch collar acts to towards lever24 and has a flange 36 and an extension 37 carrying a transverse pin 38which is received in a slot 39 in lever 24 whereby axial movement of thecore 33 pivots lever 24. A compression spring 41 is disposed coaxiallyaround rod 34 between flange 36 and the adjacent end of solenoid housing29 to hold the core 33 partially withdrawn from coils 31 when the coilsare un energized. At this position of core 33, collar 23 is adjacentmotor 13 and thus pinion gear 18 is withdrawn from engagement withengine gear 22. Upon energization of coils 31 core 33 is drawn into thecoils against the force of spring 41 and thus lever 24 is pivoted tourge collar 23 away from motor 13. Spring 27 transmits this motion ofthe collar 23 to overrunning clutch 19 and'thus to pinion gear 18 whichthen attempts engagement with engine gear 22.

Two terminals 42 at one end of housing 29 each connect with a separateone of a pair of spaced'apart contacts 43 within the housing. A movablecontact 44 on the end of core 33 serves to bridge the contacts 43 andestablish an electrical connection therebetween when core 33 has beenfully drawn into coils 31. Through electrical connections to behereinafter described, such closing of the circuit between contacts 43de-energizes pull-in coil 31a, while energization of hold-in coil 31bcontinues, and energizes the motor 13 in order to crank engine gear 22.When the engine has been started, gear 22 begins to turn faster thanpinion 18. The overrunning clutch 19 enables gear 22 to turn in thismanner while the pinion 18 is still engaged without turning motor 13.After this occurs, hold-in coil 31b is deenergized by means to behereinafter described enabling spring 41 to pivot lever 24 and draw thepinion 18 out of engagement with engine gear 22.

If a butt engagement occurs in an operator controlled system, thecondition is quickly recognized and the operator then momentarily opensthe starter circuit and then reattempts operation. As previously pointedout, in most starter motor assemblies 12, the overrunning clutch 19 andpinion gear 18 mechanism is arranged to index slightly about shaft 16with each movement of collar 23 so that the pinion gear is turned asmall amount and a butt engagement is less likely to reoccur upon thesubsequent attempt.

Many systems which are controlled by an operator rely wholly on theoperator to take the necessary steps to correct a butt engagement. It ismore desirable that this not be left to the operators judgment asoperators may exhibit undesirable delay in recognizing the condition andundesirable delay in response time. In the case of systems whereactuation of the starting system is performed automatically without thepresence of an operator it is imperative that the control circuit itselfbe capable of promptly deenergizing the solenoid coils 31 momentarily toreinitiate an attempt at engagement in the event of a butt engagement.

Considering now the means by which the starter motor assembly 12 iscontrolled to achieve these purposes, the control circuit 11 of theembodiment depicted in the drawings is of a form adapted to respondautomatically to an electrical power failure in electrical utility powerconductor 46 by cranking an engine gear 22 which may, for example, bepart of an engine driving a generator in a standby emergency electricalpower system. It will be appreciated that the system is applicable tothe starting of engines in other situations and to the starting ofoperator control systems as well although the speed and reliability ofthe circuit is less critical in connection with operator controlledengines.

Power for operating the starter motor assembly 12 is obtained from abattery 47 which in this example has a negative side connected to anegative one of the pinion solenoid terminals 32 and a negative one ofthe starter motor terminals 14. The positive terminal 14 of motor 13 isconnected to one of the terminals 42 of solenoid assembly 28 while theother terminal 42 connects with the positive side of battery 47 througha normally closed switch 48. Thus when contacts 43 are bridged bycontact 44 following energization of the solenoid 28, battery 47 isthereby connected across the starting motor terminals 14 and thestarting motor cranks engine gear 22 through pinion gear 18. As theexample of the invention being described is adapted for automaticoperation, the normally closed switch 48 is provided to open the startermotor circuit once the associated engine is operating. For this purposethe switch 48 maybe controlled by a fluid cylinder 49 having a piston 51which operates the switch 48 and which is normally spring biased to aposition at which the switch 48 is held closed. Cylinder 49 is coupledto a fluid system of the engine which becomes pressurized when theengine is operating such as the oil pump outlet. Thus when the engine isoperating and oil pressure rises piston 51 is retracted to open switch48 and thereby open the starter motor circuit. In an operator controlledsystem, switch 48 is not essential since the operator normally opens thecircuit after the engine has started by releasing the starter switch.

To energize the pinion solenoid 28, the positive one of the terminals 32is connected to the positive side of battery 47 through a normally openset of start relay contacts 52 and through the previously describednormally closed switch 48. Contacts 52 are closed by energizing of acoil 53 which has one end connected to the negative side of battery 47and has another end connected to the positive side of the batterythrough a set of normally closed relay contacts 55 of a time delay relay54 and through an additional set of normally open relay contacts 56 of apower sensing relay 57 and then through previously described normallyclosed switch 48. Within housing 29, one end of both coils 31a and 31bconnect with the positive one of terminals 32. The oposite end of pullin coil 31a connects to the terminal 42 which is connected to motorterminal 14 while the opposite end of hold-in coil 31b connects to thenegative one of terminals 32. Coil 31a has sufficiently high resistancethat motor 13 is not operated by the current transmitted through thecoil.

Accordingly, the solenoid assembly 28 is energized to commence operationof the starter motor assembly 12 upon closing of the power failuresensing relay contacts 56. This energizes start relay coil 53 throughtime delay relay contacts 55 and thereby closes contacts 52 to applybattery power across terminals 32 and thereby energizes coils 31. In theautomatic system presently being described, the relay contacts 56, whichare closed to initiate starting of the engine are normally held open bya driver coil 58 of power failure sensing relay 57 which is seriesconnected with conductor 46. Thus as long as electrical power is beingtransmitted through conductor 46, relay contacts 56 are held open. Upona power failure in conductor 46 contacts 56 close to actuate the starterassembly 12 as described above. An operator controlled system for avehicle or the like may be essentially similar except that conductor 46and coil 58 are absent and contacts 56 are a normally open starterswitch which is closed by the operator to initiate starting of theengine.

After closing of relay contacts 56 and the consequent energization ofsolenoid coils 31 as described above, pinion gear 18 is shifted axiallytowards engine gear 22. Provided that gears 18 and 22 engage properly,contact 44 connects contacts 43 and the starter motor 13 is energized toturn the engine gear. This also de-energizes pull-in coil 31a as bothends of the coil are then connected to the positive side of battery 47.Pull-in coil 31a is not needed to hold contact 44 against contacts 43 asthe forceof hold-in coil 31b is sufficient for this purpose.

Once the engine is started, cylinder 49 opens switch 48 to deenergizeall elements of the starter assembly 12 and control circuit 11. However,if a butt engagement occurs and pinion gear 18 fails to engage withengine gear 22 the elements of the circuit 11 as described to this pointwould not necessarily provide any corrective action and starting of theengine might be delayed indefinitely. To deenergize solenoid coil 31band thereby initiate a repeated attempt at gear engagement, time delayrelay contacts 55 are operated by a driver coil 59 of time delay relay54. One side of coil 59 connects with the positive terminal 42 ofsolenoid assembly 28 while the other side of the driver coil connectswith battery positive through a resistor 61, relay contacts 55, relaycontacts 56 and switch 48. A capacitor 62 is con- I nected across theends of driver coil 59 to form an RC network in conjunction withresistor 61 whereby a time delay is introduced with respect toenergization of the driver coil 59 upon the application of positivepower thereto.

Owing to the time delay required for energization of driver coil 59,time delay relay 54 does not initially affect operation of the startercircuit as described above except insofar as voltage for the start relaycoil 53 is transmitted through contacts 55. After a predetermined periodof time determined by the constants of capacitor 62 and resistor 61,coil 59 is energized sufficiently to open contacts 55 and therebydeenergize coil 53- of the start relay which in turn causes contacts 52to open to deenergize the solenoid coils 31. Spring 41 then restores thepinion gear 18 to the initial position in readiness for another attemptto engage with gear 22. Since power for energizing'coil 59 of time delayrelay 54 is supplied through the contacts 55 of the same relay, thecontacts 55 automatically reclose after being opened to initiate asecond cycle of operation. Should a butt engagement reoccur, time delayrelay 54 will again open to reset the circuit after the predeterminedtime delay period and this process will be repeated as long as isnecessary.

In the above described circuit configuration, both sides of the drivercoil 59 of time delay relay 54 are in effect coupled to a single circuitpoint at contacts 43 claims.

What is claimed is: 1. In a starter system for cranking a gear of anengine to start said engine, the combination comprising:

a source of electrical current, i an electrical starter motor, a piniongear coupled to said starter motor for rotation thereby, said piniongear being shiftable into and out of driving engagement with said enginegear,' electrically actuated means for shifting said pinion gear towardengagement with said engine gear, means for connecting said motor tosaid source of electrical current upon engagement of said pinion gearand engine gear, a set of electrical contacts which are normally closed,circuit means for connectingsaid source of electrical current to saidmeans for shifting said pinion gear through said normally closedcontacts to initiate operation of said starter system, and time delaymeans for momentarily opening said set of contacts a predetermined timeafter said means for shifting said pinion gear is connected to saidsource of electrical current, said time delay means having a firstterminal connected to said source of electrical current through said setof normally closed contacts and having a second terminal connected tosaid source through said means for connecting said source to said motorin response to engagement of said pinion gears whereby said time delaymeans ceases to conduct electrical current when said starter motor isenergized, wherein said set of normally closed contacts and said timedelay means jointly constitute a time delay relay wherein said timedelay means comprises an electrical coil disposed to open said normallyclosed contacts upon a being energized and having a first end connectedto said source of electrical current through a resistor and saidnormally closed contacts and having a second end connected to saidsource of electrical current through said means for connecting saidsource to said motor in response to engagement of said pinion gear andhaving a capacitance connected across said ends of said coil to definean RC network in conjunction with said resistor. 2. In a starter systemfor cranking a gear of an engine to start said engine, the combinationcomprising:

a source of electrical current, an electrical starter motor, a piniongear coupled to said starter motor for rotation thereby, said piniongear being shiftable into and out of driving engagement with said enginegear,

electrically actuated means for shifting said pinion gear towardengagement with said engine gear,

means for connecting said motor to said source of electrical currentupon engagement of said pinion gear and engine gear,

a set of electrical contacts which are normally closed,

circuit means for connecting said source of electrical current to saidmeans for shifting said pinion gear through said normally closedcontacts to initiate operation of said starter system, and

time delay means for momentarily opening said set of contacts apredetermined time after said means for shifting said pinion gear isconnected to said source -ceases to conduct electrical current whensaidstarter motor is energized, further comprising means for disconnectingsaid source of electrical current from said startermotor and from saidelectrically actuated means for shifting said pinion gear and from saidtime delay means in response to an operating condition of said' motor.

1. In a starter system for cranking a gear of an engine to start saidengine, the combination comprising: a source of electrical current, anelectrical starter motor, a pinion gear coupled to said starter motorfor rotation thereby, said pinion gear being shiftable into and out ofdriving engagement with said engine gear, electrically actuated meansfor shifting said pinion gear toward engagement with said engine gear,means for connecting said motor to said source of electrical currentupon engagement of said pinion gear and engine gear, a set of electricalcontacts which are normally closed, circuit means for connecting saidsource of electrical current to said means for shifting said pinion gearthrough said normally closed contacts to initiate operation of saidstarter system, and time delay means for momentarily opening said set ofcontacts a predetermined time after said means for shifting said piniongear is connected to said source of electrical current, said time delaymeans having a first terminal connected to said source of electricalcurrent through said set of normally closed contacts and having a secondterminal connected to said source through said means for connecting saidsource to said motor in response to engagement of said pinion gearswhereby said time delay means ceases to conduct electrical current whensaid starter motor is energized, wherein said set of normally closedcontacts and said time delay means jointly constitute a time delay relaywherein said time delay means comprises an electrical coil disposed toopen said normally closed contacts upon being energized and having afirst end connected to said source of electrical current through aresistor and said normally closed contacts and having a second endconnected to said source of electrical current through said means forconnecting said source to said motor in response to engagement of saidpinion gear and having a capacitance connected across said ends of saidcoil to define an RC network in conjunction with said resistor.
 2. In astarter system for cranking a gear of an engine to start said engine,the combination comprising: a source of electrical current, anelectrical starter motor, a pinion gear coupled to said starter motorfor rotation thereby, said pinion gear being shiftable into and out ofdriving engagement with said engine gear, electrically actuated meansfor shifting said pinion gear toward engagement with said engine gear,means for connecting said motor to said source of electrical currentupon engagement of said pinion gear and engine gear, a set of electricalcontacts which are normally closed, circuit means for connecting saidsource of electrical current to said means for shifting said pinion gearthrough said normally closed contacts to initiate operation of saidstarter system, and time delay means for momentarily opening said set ofcontacts a predetermined time after said means for shifting said piniongear is connected to said source of electrical current, said time delaymeans having a first terminal connected to said source of electricalcurrent through said set of normally closed contacts and having a secondterminal connected to said source through said means for connecting saidsource to said motor in response to engagement of said pinion gearswhereby said time delay means ceases to conduct electrical current whensaid starter motor is energized, further comprising means fordisconnecting said source of electrical current from said starter motorand from said electrically actuated means for shifting said pinion gearand from said time delay means in response to an operating condition ofsaid motor.